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CONTROL SYSTEMS + AUTOMATION
in energy consumption, we need to turn to the control system, its
equipment, processes, and operation.
Integrate efficient devices
More efficient devices are constantly being developed for the market.
Sometimes, the efficiency is based on a more effective process, but
sometimes it is about trying to save energy during non-operational
times. Efficiency during operation is inherent in the device and its
configuration. Integration of these devices and set-ups in the configu-
ration of the PAS helps to better configure andmaintain this efficiency.
While efficiency in production is important, there is an increasing
focus on reducing the energy used during non-operational periods
as this is waste (not used for production). For non-operational energy
savings, companies should look for open standards. ODVA provides
standards to enable a PAS to engage its energy saving modes. While
energy saving modes are part of the ODVA standards, to be very ef-
fective in their implementation, they need to be integrated back into
the PAS libraries so that energy can be saved both when the plant is
stopped and during partial process downtimes.
Implement and monitor optimised processes
More efficient processes are developed based on years of process ex-
perience. Traditionally, vendors produce PAS libraries with a focus on
achieving their process goals. An energy-aware PASwill have libraries
designed to achieve optimum energy efficiency. The libraries are also
typically pre-designed to support energy and production data
collection to ensure easy benchmarking and comparison.
The great advantage of having energy information
available within the PAS is its ability to constantly
track its energy consumption relative to the targets
identified for analysis. The effort required to execute
a process (represented by the energy consumption
level) is a valuable indicator of the progressive re-
duction in the process’ efficiency. The energy-aware
process control system can constantly track deviations
between consumed energy and the target, and provide
early indications of equipment wear or an obstruction in
the process. While we can try to save energy in many locations, the
largest energy wastage occurs during downtime. The failure of one
component or system within the plant makes production by the rest
of the system impossible, yet the energy consumption continues at
production levels. By reducing downtime, the energy-aware PAS
not only saves energy from being unnecessarily consumed, but also
uses energy information to keep the process optimised and effective.
More effective people
Frequently, many of the opportunities to improve processes lie in
improving the knowledge and behaviour of the people operating
the system. In the short term, these behaviours and knowledge
can be enhanced with training, but as employees turn over, the
most effective way to ensure energy efficient production is to build
Figure 7: Production and energy-generated data from a slow process.
Figure 8: Typical EMIS system.
The data in
Figure 7
shows the relationship between energy produc-
tion (as waste heat) and the operation time of a longer process. As
expected, the longer the process continues, the less energy is gener-
ated. The significant periods are highlighted in different colours. The
operation of a waste heat recovery system is much more complex
than a simple conveyor.
The energy-aware control system has detected the lower perfor-
mance of the system but is not able to attribute this to a specific cause
so it alerts the operator. System alarms can be caused by man-
ual operations, changes in setpoints or other factors which
are not specifically monitored so some analysis is still
required. Triggering alarms as close to real time as
possible allows the operator to minimise the likely
cause of the underperformance. The PAS is able to
detect real-time variations in energy consumption
from defined targets. This enables real-time action
to be taken to adjust the energy overconsumption
but it does not provide management with the data
they need for a higher level of analysis. To access that
data, industrial sites need an Energy Management Informa-
tion System (EMIS). The EMIS spans both the supply and demand
side analyses. For supply side analysis, the EMIS must link to tariff
schedules and analyse energy consumption against the tariffs avail-
able. For the demand side, the EMIS must link the same energy data
in the context of the production. The EMIS allows users to see longer
term trends for each system against industry benchmarks and other
systems on the site. For industrial customers, an EMIS must work
with the data from an integrated power and process system.
From opportunity to action
Energy analysis based on data froman energy-aware PASwill provide
real insight into the energy consumption of each process, and will
identify the major changes which are possible in order to reduce the
energy consumption of a control system. To achieve this reduction
Electricity+Control
July ‘16
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